A special election in southwest London triggered by a dispute over airport expansion has become the first electoral test of Prime Minister Theresa May’s handling of Britain’s divorce from the European Union.

While Zac Goldsmith quit as Conservative lawmaker for Richmond Park to run again as an independent in protest at the government’s support for a third runway at nearby Heathrow, the talk on the streets of the district is about his backing for Brexit. Sarah Olney, the pro-EU Liberal Democrat who’s his main challenger, opposes a bigger airport too, but she wants another referendum on the terms of Britain’s departure from the bloc. The Liberal Democrats held the seat until 2010 and see a chance of a comeback.

Zac Goldsmith

Photographer: Daniel Leal-Olivas/AFP via Getty Images

“If you tell the electorate what an election should be about, they have a habit of saying ‘we’ll say what it’s about,”’ former Liberal Democrat leader and Deputy Prime Minister Nick Clegg said after visiting a business in the constituency last week, when every question from workers was about Europe. “A win for us here would act as a powerful antidote to the way in which the country is being railroaded towards a hard Brexit.”

The Dec. 1 vote takes place as May, who has pledged to trigger two years of formal Brexit negotiations by the end of March, struggles to reconcile conflicting pressures. Euro-skeptics in her Conservative Party are pushing for a “hard” Brexit outside the EU single market and customs union, while others demand a “soft” break with concessions on immigration to allow freer trade.

An estimated 72 percent of voters in Richmond Park voted to remain in the EU in the June referendum, according to an analysis by Chris Hanretty at the University of East Anglia. Goldsmith, who’s running again with the support of the Conservatives and the U.K. Independence Party, is relying on his personal following, regardless of his views on Europe.

He’s carved out a reputation as a maverick in Parliament and, as a former editor of the Ecologist magazine, has championed a range of causes, including opposition to Heathrow. His supporters say they value his independence and his willingness to defy the party line.

‘Not the Normal’

“He’s not the normal run-of-the-mill Conservative, even though he’s very much hooked into the establishment,” said Mark Nellis, 56, as planes heading for Heathrow thundered over his house. “I’m probably going to vote for Zac, though previously would have been more likely to vote Labour.”

Sarah Olney

Photographer: Victoria Jones/Press Association via AP Images

Goldsmith increased his share of the vote to 58 percent in 2015 from 50 percent in 2010. With no Tory or UKIP candidate next week, he’ll avoid any split in the pro-Brexit vote. But the public backing he’s received in the campaign from pro-Heathrow, anti-EU Tory lawmaker Jacob Rees-Mogg suggests Brexit, not the airport, is at the center of the campaign, the Liberal Democrats say.

“While people feel very strongly about Heathrow, they feel disappointed, angry and uncertain about Brexit, and that’s driving how they’re going to vote in this election,” Olney said in an interview. “Zac is trying to say a vote for him as an independent will send a clear message on Heathrow; I’m saying a vote for me will send an even clearer message both about Heathrow and about Brexit.”

‘Clear and Forceful’

Goldsmith is seeking to show that he has been more effective and consistent in defending local residents from noise and pollution than Olney could be. “This is our chance as a community to send an undiluted, clear and forceful message to government,” he told a candidates’ debate on Nov. 15. “No ifs, no buts, no third runway.”

Former Prime Minister David Cameron also made a “no ifs, no buts” promise in 2009 that Heathrow would not be expanded. Goldsmith’s failure to persuade his party to stick to the promise demonstrates his impotence, according to his opponents.

“As a backbencher he had no influence at all,” said Marion McCormack, 86, who will be backing Olney. “He’s a very rich man and I think he’d be better off on his organic farm, where he used to be.”

Poll Backing

A poll of 543 Richmond Park voters last month by BMG Research for the Evening Standard newspaper suggested Goldsmith will be heading back to Parliament rather than his farm. It gave him 56 percent support, compared to 29 percent for Olney, with the main opposition Labour Party on 10 percent.

Goldsmith “has been a hard-working champion for the people of Richmond Park,” the Conservatives said in a statement explaining their decision not to run against him. “We know he will continue to be” if re-elected.

The Liberal Democrats have flooded the constituency with activists, yet the party may still have difficulty persuading people to overcome a disdain for mainstream politics that drove the Brexit vote.

“Most politicians will say one thing and do another,” said Ben Kola, 30, a heating engineer. He backs Liberal Democrat positions including wanting Britain to stay in the EU but said he won’t bother to vote. “I’d rather stress myself about doing the best for my little boy than stress about politics,” he said.